More potato virus cases suspected

The potato mop-top virus (PMTV) was found in New Zealand in September. Photo / Allied Press Files

Two cases of potato mop-top virus have been confirmed in Mid Canterbury, but many more are suspected, Biosecurity New Zealand says.

The virus, confirmed in two crops last month, was found during routine sampling of material at a cooked-chip processing facility.

However Biosecurity NZ, through tracing, now suspects 18 properties were affected and has expanded testing nationwide.

While not harmful to humans if consumed, the virus is a notifiable and unwanted organism in New Zealand.

More than 60 potato industry members, seeking information from officials on detection of the virus in potato tubers, attended a meeting in Ashburton recently on September 25.

It was the first meeting of Biosecurity New Zealand with industry representatives anywhere in the country.

Methven farmer David Gorman, who has 50ha of potato for seed, said there was concern at the meeting.

It was the early stages of the virus being known and information on it was limited.

The names and locations of the confirmed properties were not released to those at the meeting. However, Mr Gorman said growers were told it was found on processing growers' properties.

At the time there was very little known about how to control it - growers just had to be wary of powdery scabs on the skins of potatoes.

Growers in the district were keeping an eye on their crops and were being kept up-to-date with developments.

Biosecurity New Zealand said two infected cultivars from the 2017-18 season had been found in Innovator and Russet Burbank variety potatoes.

But testing of 2018-19 season Innovator, Russet Burbank and Agria variety seed potatoes was negative to date.

BNZ is working with national industry body Potatoes NZ to respond to the incident.

Following the Mid Canterbury meeting, BiosecurityNZ had also met growers, exporters and processors in Pukekohe and growers in Palmerston North earlier this month. More meetings were planned.

The virus, which causes distortions to the potato skin, deep cracking, rust-coloured arcs and streaks in the tuber flesh, was spread by soil-borne fungus but survived long-term in the potato plant or fungus. If established in fields, its spores can survive up to 20 years in the soil.

Biosecurity NZ said if widespread, it could cause productivity issues for growers and their main focus was to understand risks associated with its establishment in the country and minimise its impact with options to manage, contain or eradicate.

They were working to define and contain infection on known paddocks and processing plants.

This included focusing on processing waste contamination and disposal of solid potato waste from affected processing plants. Records of disposal were being kept by processing plants.

If established in NZ, Biosecurity NZ said it was manageable.

It was in North America and Europe and managed without causing major production problems for growers.

Anyone with a symptomatic potato please call 0800 80 99 66 or email PMTV2018Liaison@mpi.govt.nz.